1. Field of the Invention
The present invention generally relates to a refrigerant compressor and, more particularly, to a valved discharge mechanism of a refrigerant compressor suitable for use in an automotive air conditioning system.
2. Description of the Prior Art
The valved discharge mechanism in a refrigerant compressor is well known in the prior art. For example, FIGS. 2 and 3 depict a valved discharge mechanism in a refrigerant compressor as disclosed in U.S. Pat. No. 4,815,952. As disclosed therein, a refrigerant compressor includes a compressor housing defining a compression chamber in which successive strokes of intake, compression, and discharge of a refrigerant gas are repeatedly performed. Further, the compressor includes valve plate 241 which is formed to partition a compression chamber and a discharge chamber and a discharge valve assembly which is mounted on an upper surface of valve plate 241. Valve plate 241 has discharge hole 244 extending therethrough for communicating the compression chamber with the discharge chamber. The discharge valve assembly includes discharge reed valve 249 and valve retainer 250 which are secured together to the upper surface of valve plate 241 by fixing bolt 255. Valve seat 241a is integrally formed in the upper surface of valve plate 241 around discharge hole 244. Discharge reed valve 249, which is made of an elastic material, regulates a flow of the refrigerant gas and is in sealing contact against valve seat 241a without an air gap when operation of the compressor is stopped.
Valve retainer 250 limits the bending movement of discharge reed valve 249 in the direction in which the refrigerant gas exits discharge hole 244. Discharge reed valve 249 bends as it opens and closes discharge hole 244 and has a spring constant which allows discharge reed valve 249 to block discharge hole 244 until the pressure in the compression chamber reaches a predetermined value.
Spiral elements 242, 252 are disposed within the compressor housing and interfit with an angular and radial offset. At least one pair of fluid pockets are thereby defined between spiral elements 242, 252.
The air gap between discharge reed valve 249 and the upper surface of valve seat 241a is increased and decreased in accordance with the velocity of the refrigerant gas exhausted from the discharge chamber through discharge hole 244. The discharge velocity varies according to the rotational speed of the compressor. It will be appreciated by those skilled in the art that compressed air in the fluid pockets is intermittently delivered to a central fluid pocket. This, in turn, leads to pulsed fluid delivery through discharge hole 244. As compressed refrigerant gas is discharged through discharge hole 244, a resulting Karman vortex street causes vibration of the compressed refrigerant gas. When the magnitude vibration of the compressed refrigerant gas reaches a frequency band of approximately 10-14kHz, the air gap, which is formed as a column of air, produces a resonant vibration due to sympathizing with the vibration of the compressed refrigerant gas. As a result, an offensive noise propagates to the passenger compartment of the vehicle.